Microwave ovens are coming into increasing use and it is stated by some that by 1980, one-fourth of all kitchens will have one. The widespread use of microwave ovens as a convenient and rapid cooking device has caused some problems in food packaging. Many of the convenience foods which could be advantageously cooked in microwave ovens are presently packed in aluminum trays which are suitable for use in regular ovens, but, are unsuitable for microwave ovens since, as is well known, microwaves bounce off metal and the deflected microwaves cause uneven cooking.
As a consequence, the food industry, to avoid packaging the same product in two different type containers, one for microwave and one for conventional ovens, has turned to containers made of special paper which is suitable for use in both types of ovens.
One style of container used for packaging, shipping, and cooking convenience foods in ovens in such container comprises a tray having sides that are sloped inwardly, thus forming a package tray which has an opening at the top that is smaller in diameter than its base. Such trays are difficult to handle during shipping inasmuch as the sloped side walls do not allow compact side-by-side stacking for shipping and storage purposes. Further, special covers are required for such trays because the side walls, which slope inwardly, do not hold themselves in their set-up configuration and require a cover which centers the tray within the cover and maintains the tray in its tapered configuration. Such special covers, when formed from more than one blank, means extra labor and costs which, of course, is borne ultimately by the consumer.